This invention relates to a magnetic recording and reproducing apparatus such as a time lapse magnetic recording and reproducing system (hereinafter referred to as a xe2x80x9ctime lapse VTRxe2x80x9d) for recording and reproducing picture signals while intermittently skipping frames, which is used for monitoring, burglar-proofing, and so forth.
Recently, a time lapse VTR which can make long time recording such as 720 hours on a single tape by sequentially switching picture signals from a plurality of video cameras and recording them while intermittently skipping frames has gained a wide application so as to simultaneously monitor various places such as plants, sites of construction, shops, etc., in place of guards. When any accident occurs, valuable information can be acquired by quickly reproducing the picture signals recorded on the tape.
JP-A-62-295581, for example, discloses a time lapse VTR which counts the number of tracks on a magnetic tape at the time of reproduction of the tape, extracts reproduction signals from the tape in one field or frame unit whenever the count value becomes equal to the number of video cameras, alternately records the outputs of a plurality of video cameras in one field or frame unit on the same magnetic tape, takes out the outputs of the desired video camera or cameras in one field or frame unit from the magnetic tape at the time of reproduction, and can thus confirm correctly the recorded content.
Next, the construction of a time lapse VTR using a video cassette tape of a VHS system and available commercially in the past will be explained by way of example with reference to the accompanying drawings.
FIG. 1 shows an example of the construction using the conventional time lapse VTR. In FIG. 1, reference numeral 1 denotes a time lapse VTR, 2 is a switcher and 3a to 3d are video cameras. Picture signals from the video cameras 3a to 3d (A, B, C and D ch (channels), respectively) are sequentially switched in a field or frame unit by a picture switching circuit 4 of the switcher 2 and are supplied to the time lapse VTR 1. Though the switcher 2 is shown separately disposed in another apparatus, it may be assembled into the time lapse VTR 1. A chrominance signal in the inputted picture signals is converted to a low band signal by a color low-pass conversion circuit 7 in the time lapse VTR 1, while a luminance signal is subjected to frequency modulation by an FM modulation circuit 8. The outputs of these circuits 7 and 8 are added by an addition circuit 9, and each channel is sequentially recorded by four magnetic heads H1+(12), H2xe2x88x92(13), H3xe2x88x92(14) and H4+(15) mounted on a cylinder 11 on a magnetic tape 16xe2x80x2 through a recording amplifier 10. In this case, operation modes include a normal speed mode (33.33 mm/sec in a standard mode of the VHS system, for example) for recording and reproduction while the tape is continuously transported run at a normal speed, and besides an intermittent recording/reproduction mode (recording while the tape is stopped) for long time recording by intermittently transporting the tape. During reproduction, the reproduction head signals from the magnetic heads H1+(12), H2xe2x88x92(13), H3xe2x88x92(14) and H4+(15) are amplified by preamplifiers 16, 17, 18 and 19, respectively, are then passed through switch circuits 20, 21, 22, are converted to chrominance signals and luminance signals restored to their original bands by a color high-pass conversion circuit 23 and an FM demodulation circuit 24, and are further added together by an addition circuit 25 to provide reproduction picture signals. System control means 27 activates a servo circuit 30 which controls the cylinder 11, a control head 28 and a capstan shaft 29 in accordance with an operation mode inputted by a user through mode setting/input means 26, and lets it control the operation condition of the time lapse VTR. The system control means 27 activates a change-over circuit 31, selects one of the outputs of the switch circuits 20 and 21 as the output of the switch circuit 22 in the normal speed reproduction mode of the tape, and selects the one of the outputs of the switch circuits 20 and 21 which has the higher level as the output of the switch circuit 22 under control of a level detection circuit 32 during a search reproduction mode in which the recorded content can be watched more quickly than the normal speed.
The switcher 2 divides the picture signal from the time lapse VTR1 into field units by A/D means 33, an image memory 34, D/A means 35 and memory control means 36 which controls these circuit elements and a reproduction picture of a desired channel can thus be obtained on a TV monitor 38 in accordance with the output of reproduction channel setting means 37.
Here, when a tape which is intermittently recorded is reproduced intermittently, a substantially flat and satisfactory reproduction head signal such as shown in (e) or (f) in FIG. 2 can be obtained on the basis of a SW30 signal 39 representing the period in which the magnetic heads 12 to 15 are in contact with the tape as shown in (b) in FIG. 2. Needless to say, a substantially flat and satisfactory reproduction head signal can likewise be obtained as shown in (e) or (f) in FIG. 2 when a tape recorded at the normal speed is reproduced at the normal speed. When the tape recorded intermittently is reproduced at the normal speed and this is watched somewhat quickly, a head reproduction head signal above a necessary level can be obtained, although the waveform becomes diamond-like as shown in FIG. 3 because the tilt of the recording track and the reproduction trace is different by one track. Accordingly, the reproduction picture of each of the A, B, C and D channels selected through the switcher 2 can be obtained satisfactorily in both of these cases.
In the conventional time lapse VTR described above, however, the reproduction trace orbit of the magnetic heads stretches over six tracks at the time of 5-time speed search as shown in FIG. 4 by way of example in a search reproduction mode in which a tape of intermittent travel multi-channel recording is transported at a high speed. In this case, the outputs of the switch circuits 20 and 21 become diamond-like as shown in (f) and (g) in FIG. 5 and a level detection circuit 32 selects the output which has the higher level, so that the output of the switch circuit 22 becomes such as shown in (h) in FIG. 5. Assuming that 4-channel picture signals are recorded by four cameras, the output of the switch circuit 22 includes A, B, C and D channels that partially exist in one reproduction field as shown in (i) in FIG. 5. In other words, each channel is reproduced partially on the TV monitor 38 as shown in FIG. 6 in such a manner as to correspond to the of output of the switch circuit 22 shown in (h) in FIG. 5. Eventually, the A, B, C and D channels are multiplexed as shown in FIG. 7 and the resulting picture becomes extremely difficult to watch.
It is a main object of the present invention to provide a VTR which makes it possible to recognize and confirm easily and correctly a reproduction picture not only when a tape intermittently recorded is reproduced intermittently or at a normal speed but also in search reproduction for watching more quickly a recorded content, irrespective of recording modes such as intermittent recording and normal speed recording.
It is another object of the present invention to watch simultaneously, quickly and satisfactorily reproduction pictures of a large number of channels by displaying dividedly pictures of a plurality of channels on a monitor during search reproduction.
It is still another object of the present invention to watch sequentially, quickly and satisfactorily reproduction pictures of a large number of channels by displaying dividedly pictures of a plurality of channels on a time division basis at the time of search reproduction.
To accomplish the objects described above, the present invention disposes picture switch means for switching picture signals inputted from a plurality of video cameras in a field or frame unit and converting them to one continuous picture signal; recording picture information generation/addition means for generating recording picture information signals such as the total number m of the channels of the video camera outputs combined as one continuous picture signal, each channel number, etc., and adding the information signal to one continuous picture signal described above at the time of recording; four magnetic heads forming two magnetic head pairs (so-called xe2x80x9cdouble azimuth headsxe2x80x9d) having mutually different azimuth angles xcex1 and xcex2 (generally xcex1=+xe2x8ax96, xcex2=xe2x88x92xe2x8ax96) and so disposed adjacent to one another on a cylinder as to oppose one another at about 180xc2x0 (a pair of H1+, H2xe2x88x92 and a pair of H3xe2x88x92, H4+), for recording and reproducing the continuous picture signals to which the recording picture information signal is added; reproduction signal processing circuit means for reconstructing and reproducing original picture signals from reproduction head signals generated by selecting and switching the outputs from the four magnetic heads; recording picture information detection means for detecting the added recording picture information from the reproduction picture signals at the time of reproduction; system control means for controlling the operation mode of the time lapse VTR in accordance with the operation condition inputted and set by a user such as intermittent recording, normal speed recording, intermittent reproduction, normal speed reproduction, search reproduction, etc; and servo means for optimally setting and controlling a speed multiple k to the normal tape travelling speed in accordance with the total number m of the detection channels from the recording picture information detection means at the time of search reproduction from the mode signal output from the system control means.
The present invention disposes image memory means for once converting reproduction picture signals from analog signals to digital signals, writing them into an image memory, and later converting the signals from the digital signals to the analog signals and reading them out; write period control means for generating and outputting a control signal of a write period into the image memory in accordance with the output from the recording picture information detection means for generating and comparing two sets of reproduction head signals (a set of H1+, H3xe2x88x92 and a set of H2xe2x88x92, H4+, or a set of H1+, H4+ and a set of H2xe2x88x92, H3xe2x88x92) from the outputs of the magnetic heads; write control means for controlling write into the image memory; and read control means for controlling read from the image memory.
Further, the image memory means is provided with a plurality of image memory regions corresponding to recording signals of multiple channels and with read/thinning-out processing means for thinning and reading out from a plurality of image memory regions in horizontal and vertical directions.
The image memory means is provided with write/thinning-out processing means for thinning out and writing into the image memory region in accordance with the write period control signal for each channel.
The picture signals from each video camera are selected in the field or frame unit by the switcher means and are converted to a series of continuous picture signals, and then the recording picture information addition means adds the picture information such as the total number m of each picture signal incorporated in the continuous picture signal, each channel number, etc., in the field or frame unit to the vertical retrace line period of the continuous picture signal, for example, and is thereafter recorded by the magnetic heads on the magnetic tape.
At the time of reproduction, the reproduction signal processing circuit means selects and switches the outputs from the four magnetic heads and generates a reproduction head signal, and this reproduction head signal is restored and demodulated to the original picture signal. On the other hand, the recording picture information added at the time of recording is detected from the reproduction picture signal by the recording picture information detection means, and the total number m of the channels thus detected is outputted to the servo means and to the write period control means. The servo means optimally sets and controls the speed multiple k to the normal tape travelling speed at the time of search reproduction in accordance with the operation mode set by the user using the system control means and with the total number m of the detection channels from the recording picture information detection means, so that a search reproduction picture can be obtained on the entire surface of the screen of the monitor TV in all the recording channels.
The write period control means described above generates two sets of reproduction head signals (a set of H1+, H3xe2x88x92 and a set of H2xe2x88x92, H4+, or a set of H1+, H4+ and a set of H2xe2x88x92, H3xe2x88x92) from the outputs of the magnetic heads, and further generates a control signal representing the write period into the image memory in accordance with the total number m of the detection channels from the recording picture information detection means, each channel number and a search direction signal representing a search direction (a positive or reverse direction) from the system control means on the basis of the reproduction head signals described above. Accordingly, the write control means controls a write operation to a predetermined portion of the image memory means in accordance with this write period control means, so that the reproduction picture signal portion of only a specific desired channel can be written into the image memory means from the picture signals in which each channel is continuously reproduced. Next, the read control means controls sequentially a read operation of the picture signals from the image memory means storing only the specific channels, so that a search reproduction picture of only a specific desired channel can be obtained without multiplex-reproduction of each channel, and a recording content which is extremely easy to watch can be retrieved and confirmed at an extremely high speed.
Here, when the set of H1+, H3xe2x88x92 and the set of H2xe2x88x92, H4+ are used as the two sets of the reproduction head signals, the magnetic head output having an extremely high level is selected as the reproduction head signal from among the magnetic heads H1+, H2xe2x88x92, H3xe2x88x92, H4+ and is demodulated to the original picture signal. The write period control signals for each channel are generated in such a form in which they are taken off for only the period of each count value obtained when counting is made in every m in the case of positive direction search, for example, in accordance with the total number m of the detection channels and with the search direction signal on the basis of the number of state of High and Low of a first xcex1 azimuth signal (High representing the xcex1 side) or a first xcex2 azimuth signal (High representing the xcex2 side; an inversion signal of the first xcex1 azimuth signal) reproducing a reproduction head period of an azimuth angle on only the xcex1 side or the xcex2 side and generated from the comparison signal of the two sets of the reproduction head signals (the set of H1+, H3xe2x88x92 and the set of H2xe2x88x92, H4+) and the SW30 signal described above. Accordingly, the reproduction picture signals of each channel can be written into the image memory for each channel at the time of search reproduction, and the full screen search reproduction picture can be obtained for each channel. In this case, when the total number m of the detection channels is expressed as the product of prime numbers Pn in accordance with the following equation by expressing the search speed multiple k irrespective of the tape travelling speed at the time of recording (for example, the tape stop condition during intermittent travelling, the tape continuously travels during normal travelling, and the inclination of the recording tape pattern is somewhat different)
m=P1l1xc2x7P2l2xc2x7P3l3xc2x7. . . xc2x7Pnlnxe2x80x83xe2x80x83{circle around (1)}
(where ln is a natural number),
then, a reproduction picture can be obtained throughout the full screen of the TV monitor by satisfying the following relationship 2:
kxe2x89xa0axc2x7Pnxe2x80x83xe2x80x83{circle around (2)}
(where a is an integer exclusive of 0, and a negative sign represents the opposite direction search).
When the set of H1+, H4+ and the set of H2xe2x88x92, H3xe2x88x92 are used as the two sets of the reproduction head signals, the outputs of the magnetic heads H1+, H4+ or the outputs of the magnetic heads H2xe2x88x92, H3xe2x88x92 are selected as the reproduction head signals, and they are demodulated to the original picture signals. The write period control signal for each channel is generated in the following way in accordance with the total number m of the detection channels on the basis of a second xcex1 azimuth signal and a second xcex2 azimuth signal exhibiting the state change of High and Low when the waveforms of the two sets of the reproduction head signals (the set of H1+, H4+ and the set of H2xe2x88x92, H3xe2x88x92) become substantially zero, and at each shift point of the recording track. In other words, when the total number m of the detection channels is even-numbered, the write period control signals are generated in such a form in which they are taken off for only the period of each count value obtained by counting the state numbers High and Low of the second xcex1 azimuth signal and the second xcex2 azimuth signal in every m/2 unit. In this case, the full screen search reproduction picture of each channel can be obtained using both of the two sets of the reproduction head signals (the set of H1+, H4+ and the set of H2xe2x88x92, H3xe2x88x92). When the total number m of the detection channels is odd-numbered, the write period control signals for each channel are generated in such a form in which they are taken off for only the period of each count value obtained by counting the state numbers High and Low of the second xcex1 azimuth signal or the second xcex2 azimuth signal in every m unit. In this case, the full screen search reproduction picture can be obtained by using either one of the two sets of the reproduction head signals (the set of H1+, H4+ and the set of H2xe2x88x92, H3xe2x88x92) or can be obtained more quickly by using both of them. When the total number m of the detection channels is expressed as the product of a prime number Pn, 2 and 4 in accordance with the following equation by expressing the search speed multiple by k, irrespective of the tape travelling speed at the time of recording,
m=2xc2x74l0xc2x7P1l1xc2x7P2l2xc2x7P3l3xc2x7 . . . xc2x7Pnlnxe2x80x83xe2x80x83{circle around (3)}
(where ln is a natural number),
a reproduction picture can be obtained throughout the full screen of the TV monitor by satisfying the following relational formula
kxe2x89xa0axc2x7Pnxe2x80x83xe2x80x83{circle around (4)}
(where a is an integer exclusive of 0, a negative sign represents a reverse direction search, and P0=4).
However, in the case of k=3 speed multiple, a satisfactory search reproduction picture can be obtained for all the channels by deviating the trace positions of the magnetic heads, that is, tracking.
Further, when the picture information of each channel stored in the first, second, third and fourth memory regions is sequentially thinned out in both horizontal and vertical directions and are read out by the image memory means, a picture of a plurality of channels can be dividedly displayed on the monitor at the time of search reproduction, and search reproduction pictures of a large number of channels can be watched simultaneously and quickly. Multiple division monitor display can also be made at the time of search reproduction by storing sequentially the picture information of each channel while thinning them out in both horizontal and vertical directions and then reading them out sequentially.